2019-03-21T18:27:28ZAntimicrobial susceptibility, resistance determinants and molecular epidemiology of Neisseria gonorrhoeae in Irelandhttp://hdl.handle.net/2262/86065
Antimicrobial susceptibility, resistance determinants and molecular epidemiology of Neisseria gonorrhoeae in Ireland
RYAN, LAURA
High-level resistance to and treatment failures with ceftriaxone and azithromycin, the first line agents for treatment of gonorrhoea are reported and antimicrobial-resistant N. gonorrhoeae is now an urgent public health threat. This study investigated rates of resistance to extended-spectrum cephalosporins (ESCs), azithromycin and other agents among gonococci in Ireland, resistance mechanisms and molecular epidemiology of the most resistant subset of isolates.
Six-hundred and nine isolates from 4 different tertiary referral hospitals in Ireland were recovered for susceptibility testing against extended-spectrum cephalosprorins, azithromycin, ertapenem, ciprofloxacin, gemifloxacin, penicillin, tetracycline, spectinomycin, gentamicin and fosfomycin by gradient MIC strip. Forty-three isolates were selected for whole-genome sequencing based on elevated MICs, in particular to extended-spectrum cephalosporins and azithromycin. Sequencing libraries of N. gonorrhoeae genomic DNA were generated using the NexteraXTTM library preparation kit according to manufacturer?s instructions and sequenced on an Illumina MiSeq instrument. The NG-STAR database, pubMLST tool and ARG-ANNOT database were employed for data analysis.
Seven high-level azithromycin resistant (HLAzi-R) isolates were identified, while no resistance to ceftriaxone was found. All isolates were susceptible to spectinomycin. 98.2%, 33% and 9.7% of isolates were non-susceptible to penicillin, ciprofloxacin and tetracycline, respectively. MIC90 for ertapenem, gemifloxacin, gentamicin and fosfomycin were 0.032 mg/L, 2 mg/L, 8 mg/L and 32 mg/L, respectively.
Mosaic penA alleles XXXIV, X and non-mosaic XIII were associated with elevated ESC MICs. L421P mutation in ponA, G120K plus A121N/D/G alterations in penB (encoding PorB), H105Y alteration in mtrR and A deletions in the mtrR promoter were also associated with reduced susceptibility to ESCs. A2059G and C2611T mutations in 23s rRNA alleles were associated with HLAzi-R and gonococci with azithromycin MICs of 4-32 mg/L, respectively. The 43 isolates belonged to 31 NG-MAST STs and most prevalent MLST STs included ST1580, ST9396 and ST1901. All HLAzi-R isolates belonged to MLST ST1580, among which some clonal clustering was observed. When these isolates were compared to HLAzi-R isolates from a UK outbreak, analysed at a whole-genome sequence level, they differed significantly.
This is the largest genomic study of Irish N. gonorrhoeae performed to date. Ceftriaxone remains a suitable empiric agent for treatment of gonorrhoea in Ireland. A number of potential alternative agents were identified. There was good correlation between previously described genetic mutations and phenotypic susceptibility categories for ESCs and azithromycin and N. gonorrhoeae. This work highlights the advantages and potential of whole-genome sequencing to be applied at scale in the surveillance of antibiotic resistant strains of N. gonorrhoeae, both locally and internationally.
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2019-01-01T00:00:00ZPostprandial Cardiometabolic risk in Autoimmune Thyroid Disease and Type 1 Diabetes Mellitushttp://hdl.handle.net/2262/86001
Postprandial Cardiometabolic risk in Autoimmune Thyroid Disease and Type 1 Diabetes Mellitus
MCGOWAN, ANNE NOELLE
Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide. Atherosclerosis is implicated in the development of CVD. Postprandial lipaemia is independently predictive of atherogenesis and of future cardiovascular events. Postprandial studies can unmask lipoprotein abnormalities not present in the fasting state. The overall CVD risk is increased in overt hypothyroidism (OH) and possibly in subclinical hypothyroidism (SCH). LDL-Cholesterol (LDL-C) is increased in OH but not SCH, which may partly explain the increased CVD risk in OH, but likely does not entirely explain it. It is not consistently clear what happens to triglyceride and HDL-Cholesterol (HDL-C) in OH and is even less clear in SCH. Hence, our hypothesis for the Thyroid study: Postprandial dyslipidaemia is associated with lipoprotein derangements that may contribute to the increased cardiovascular risk observed in hypothyroidism in addition to that conferred by fasting LDL-C concentrations ? To examine fasting and postprandial HDL-C metabolism in both OH and SCH in an effort to elucidate the differences observed between OH and SCH. In order to test these hypotheses, a clinical study was undertaken. The thyroid study was a cross-sectional study with 21 OH, 28 SCH and 44 controls. Plasma lipids with particular emphasis on intestinally derived lipoproteins (ApoB48), HDL cholesterol (HDL-C) and endothelial function, as assessed by flow-mediated dilatation (FMD) of the forearm were measured fasting and postprandially. The original findings of these studies are that ApoB48 was increased postprandially in OH and to a lesser degree in SCH compared to a matched control group. FMD was decreased in OH only. In addition, HDL-C was significantly lower postprandially in SCH only and CETP associated HDL-C was decreased in OH, which may account for the preserved HDL-C observed in this cohort. In conclusion, postprandial lipoprotein and vascular abnormalities differ between OH and SCH. Although both are characterized by increased intestinally derived lipoprotein particles, HDL is reduced only in SCH. Maintained HDL in OH probably reflects reduced CETP activity, which was not observed in SCH. Postprandial endothelial dysfunction is abnormal only in OH and this effect does not appear to reflect increased inflammation. These findings give additional insight into the pathophysiology of CVD associated with hypothyroidism. The overall CVD risk is increased in type 1 diabetes mellitus (T1DM) and individuals with T1DM have accelerated atherosclerosis. Endothelial dysfunction precedes the development of atherosclerosis. Yet, in the presence of good glycaemic control, individuals with T1DM have a relatively preserved fasting and even favourable lipid profile. It is not known to what extent postprandial lipoprotein changes contribute to the increased CVD risk. Hence, our hypothesis for the T1DM study: Postprandial dyslipidaemia is associated with lipoprotein derangements and endothelial dysfunction that may contribute to the increased cardiovascular risk observed in T1DM. Elucidate what glucometabolic and lipoprotein factors affect endothelial dysfunction in T1DM. In order to test these hypotheses, a clinical study was undertaken. The T1DM study was a cross-sectional study with 20 T1DM and 24 controls. Additional controls subjects (n=98) were studied to further explore variables associated with endothelial function. Plasma glucose and lipids with particular emphasis on intestinally derived lipoproteins (ApoB48) and endothelial function, as assessed by flow-mediated dilatation (FMD) of the forearm were measured fasting and postprandially. The original findings of these studies are that ApoB48 was increased fasting and postprandially in T1DM only. Fasting FMD did not differ between groups but decreased significantly postprandially in T1DM subjects only. Analysis of the matched group (n=44) and the pooled data (n=142) revealed a positive correlation between peak glucose concentration and overall percentage FMD change and an inverse correlation between AUC HDL-C and percentage postprandial FMD change. To conclude, postprandial lipoprotein and vascular abnormalities differ in T1DM compared to matched controls, resulting in endothelial dysfunction. These changes are possibly mediated through postprandial glucose excursions and maybe attenuated by HDL-C.
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2019-01-01T00:00:00ZThe nerve of facial expression, impact of its anatomical variations on iatrogenic surgical injury and a novel MRI diffusion weighted imaging technique to image its intra-parotid coursehttp://hdl.handle.net/2262/85541
The nerve of facial expression, impact of its anatomical variations on iatrogenic surgical injury and a novel MRI diffusion weighted imaging technique to image its intra-parotid course
EL KININY, WALID HOSAM
This doctorate in clinical medicine set out to assess how variations in facial nerve anatomy to the intra-parotid venous system could impact on surgical access to the parotid gland or the mandible, and explored methods to help reduce the risk of iatrogenic facial nerve injury. The vast majority of surgical descriptions in parotid or extra-oral mandibular surgery rely on the normally described relationship of the facial nerve to predefined surgical landmarks and intra-parotid venous structures.
Published reports on the incidence of the iatrogenic facial nerve injury vary widely according to speciality and institutions. What is known is that multiple specialities require the skills and knowledge to operate safely in or around the parotid gland where the extra-cranial facial nerve is put at risk. A recent systematic review of maxillofacial extra-oral access to the mandibular condyle, involving eight-multicentre studies showed incidence of iatrogenic facial nerve injury of up to 11%, with some studies suggesting incidence rates of up to 42% with particular approaches. The impact of anatomical variation on surgical technique was not considered in any of the reports and neither was the potential for preoperative imaging of the facial nerve.
Imaging of the extra-cranial facial nerve has historically been extremely difficult despite the wide availability of imaging methods available today. Diffusion weighted magnetic resonance imaging of intracranial white-matter tracts has shown great success in recent years. The application of this method of imaging of extra - central nervous system neural tracts is now being explored. This doctorate aims to assess the feasibility of reproducing the facial nerve white-matter tract as it courses through the parotid gland.
The first arm of this doctorate research project involved detailed dissections of the facial nerve in a cohort of cadaveric subjects donated to the anatomy department of Trinity College Dublin. Facial nerve variation to predefined surgical landmarks was analysed with respect to potential impact on surgical technique. With respect to the 'safe zone' utilised in making a pre-auricular incision, a 'safe zone' of 6mm was identified between the most anterior point of the external auditory meatus and the most posterior branch of the temporal nerve. As such, 6mm is the distance advocated by this study, marking a reduction in the distance previously advocated and currently widely practised whereby it would be safe to make a pre-auricular incision to access the parotid gland or the temporomandibular joint while avoiding inadvertent damage to the temporal branch of the facial nerve.
Additionally, as part of the first arm of this project, intra-parotid venous structures and their relations to the facial nerve were analysed with respect to potential impact on surgical technique. A novel, previously unreported variation of the facial nerve and the superficial temporal vein was discovered, and subsequently published.
The second arm of this doctorate research project involved cadaveric diffusion weighted magnetic resonance imaging of the head and neck, followed by detailed dissections of the facial nerve. Extra-cranial facial nerve tracts were identified and anatomically validated. The imaging parameters used were successfully applied to live subjects with disease free parotid glands, thereby proving the feasibility of imaging the extra-cranial facial nerve tract. The profound clinical implications of this are elaborated, especially in the context of helping avoid iatrogenic facial nerve injury, where prevention far outweighs the limited and arduous possibility of nerve repair and cure.
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2018-01-01T00:00:00ZExamining links between Factor Xa, endothelial dysfunction, adverse pregnancy outcomes and cardiovascular disease in Lupushttp://hdl.handle.net/2262/85521
Examining links between Factor Xa, endothelial dysfunction, adverse pregnancy outcomes and cardiovascular disease in Lupus
MURPHY, CLAIRE-LOUISE MARIE
Systemic lupus erythematosus (SLE) is a multisystemic autoimmune rheumatic disease (ARD) associated with significant morbidity and mortality, which presents mainly in women of childbearing age. Women with SLE have a 5-10-fold increased risk of developing cardiovascular disease (CVD) compared to age and sex-matched controls. Increased CVD risk in SLE is not fully explained by traditional risk factors and other factors such as persistent inflammation, autoantibodies and microparticles (MPs) have been implicated. Women with SLE and previous adverse pregnancy outcomes (APO) are at increased risk of CVD. Other co-morbidities in women with SLE include low bone mineral density (LBMD), which is also linked with CVD. Increasing interest has focused on the involvement of serine proteases (SP) such as anti-Factor Xa (FXa) and anti-Thrombin (Thr) in atherosclerotic plaque formation. These SP are of further interest because they are known to have extended cellular/inflammatory effects beyond coagulation through their activation of protease activated receptors (PARs) and antibodies (IgG) directed against them have been identified in patients with SLE.
To examine the importance of these risk factors in CVD pathogenesis in SLE, I studied a cohort of 100 patients with SLE who had undergone detailed vascular imaging via carotid and femoral ultrasound scans. These patients had no clinical diagnosis of CVD prior to scanning and were subdivided by the presence of subclinical CVD (n=36) and absence of CVD (n=64). I explored associations between atherosclerotic plaque and the presence of anti-FXa and/or anti-Thr IgG by ELISA. Plasma was analysed for presence of endothelial and platelet microparticles (EMPs and PMPs). Samples were stained with Annexin V, CD42a, CD31, CD105 and CD144 and measured using flow cytometry. Furthermore, I carried out retrospective analysis of the pregnancy experience of 95 women with SLE focusing on APO and CV risk. I then correlated bone density results with CV status. Finally, I carried out a systematic review to determine whether fertility and parity are reduced in patients with SLE.
Of the cohort 95% were female with a mean age of 45.2 (range 20-66; SD 12.4) years. Anti-FXa IgG positivity was found in 33/64 (52%) of patients without plaque and 11/36 (31%) of patients with plaque (p=0.04). PMPs were higher in patients with SLE compared to healthy controls (p=0.025). Strikingly, almost half the women (45%) with SLE had no children, more than double one would expect in UK women of the same mean age. A total of 61% had APO and rates of miscarriage were higher (31%) than in the general population (15-20%). My systematic review showed an overall reduction in fertility and parity in women with SLE. Of this lupus cohort, 81% had available bone density scans and 65% had LBMD.
This work demonstrates for the first time that anti-FXa IgG may be atheroprotective in patients with SLE. PMPs are higher in patients with lupus, likely due to overall disease burden. APO and miscarriage rates were high which is in keeping with other studies. My study identified much higher rates of nulliparity in women with SLE than in the general population. Reasons underlying this difference are likely to be multifactorial. The systematic review revealed reduced fertility and parity in women with SLE, although this was confounded by differences in design and outcome measures of studies selected for inclusion. Although there was no correlation between lupus and CVD with low BMD, my work has highlighted the importance of screening for osteoporosis in lupus. Overall, the work produced in my thesis has contributed to the identification of risk factors for CVD in patients with SLE. Further research is now required to elucidate the mechanisms involved in SLE CVD progression.
APPROVED
2018-01-01T00:00:00Z